If you're up for a real DIY challenge, Instructables user DIY-Create has one for you: he went to his local junkyard, picked out two comfortable but definitely old car seats from a 1974 Datsun (now Nissan) 240z, and hit the workshop to restore the seats and turn them into office chairs. It's a lot of work, but it's definitely doable.

DIY-Create notes that he's a big Top Gear fan, so it made sense to him to try and use car sets in his office. They may not be prized for ergonomics or features like our favorite office chairs, but they're definitely cheaper and comfortable. You'll definitely need some equipment and parts for this, and the total list came up to around $300, not including any tools DIY-Create already had in his workshop.

You spend hours at a time at your desk, so hopefully you're sitting in a comfortable chair. If …
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Even he admits that this project was challenging and definitely not worth the effort for most people, but he also says he learned a lot, so if you're interested in an ambitious DIY project that can yield some good-looking and useful results, this might be one to try. Check out the whole process from start to finish at the link below.